1. Field of the Invention
Embodiments relate to an image sensor including phase difference detection pixels and an image pick-up apparatus including the same.
2. Description of Related Art
With the increase in demand for high-quality image acquisition technology in an image acquisition apparatus, such as a camera, an auto focus (AF) system has been increasingly applied to cameras for mobile phones or small-sized mobile devices as well as digital cameras and interchangeable lens cameras.
A phase difference detection type AF system or a contrast detection type AF system is mainly used as the AF system.
In the contrast detection type AF system, high frequency data are extracted from image data acquired by an image sensor, and AF control is performed to maximize the high frequency data. To this end, a signal processing circuit is required. However, an additional sensor or an optical system is not needed. Consequently, the AF system may be configured at relatively low cost. However, the contrast detection type AF system is slower and less accurate than the phase difference detection type AF system.
In the phase difference detection type AF system, light incident through a pick-up lens is pupil-divided into a pair of images, and a phase difference, which is an interval between the images, is detected to set the position of the pick-up lens, thereby detecting focus.
In the phase difference detection type AF system, a phase difference detection AF sensor may be provided separately from the pick-up lens, or phase difference detection pixels may be arranged in an image sensor.
In the phase difference detection type AF system, some regions of the phase difference detection pixels are shielded to receive a limited amount of incident light. In a case in which the shielded regions of the phase difference detection pixels are the same on the left and right, the quantities of light received from a pair of phase difference detection pixels having different shielding directions are different from each other for the phase difference detection pixels arranged at an outer region of the image sensor as compared with the central region of the image sensor.
AF accuracy based on phase difference is lowered due to the difference in quantity of incident light.